Christian belief does not require 4,000 year old polytheistic - pantheistic Hindu termonology. Today, the use of "namaste" is found on the Nepal and Indian subcontinent, Southeast Asia and among the Indian diaspora worldwide.

The gesture (but not the term namaste for it) is a sacred Hindu symbol widely used as a greeting in the parts of Southeast Asia where Indian religions are strong. Namaste is usually spoken with a slight bow and hands pressed together, palms touching and fingers pointing upwards, thumbs close to the chest. This gesture is called añjali mudrā; the standing posture incorporating it is pranamasana.

Praṇāma is a form of respectful or reverential salutation before something, or another person – usually a deity. It is found in Indian culture and Hindu traditions; the meaning of Sana is "light, brilliant, radiant; praise."

Namaste is a Sanskrit Hindu acknowledgement in India, meaning "I bow to the divine in you, and is a gesture to send a message of peaceful spirituality to the universe hoping to receive back a positive message.

"Namaste" is the common greeting in the four thousand year old Hindu spiritual exercise known as yoga, where most westerners/i.e., Americans say "namaste" as a means to thank their teacher or use as an expression of relief upon the ending of the class, and are unaware of any further meaning.

According to the Webster dictionary, the word namaste, pronounced "NUHM-uh-stay," combines two phrases to mean “I bow to you,” literally understood as “The divine in me bows to the divine in you.”

It consists of a Sanskrit noun namah, meaning, "adoration, bow" (derived from the verb namati, which means, "he or she bends, or bows"), and the pronoun te meaning, "to you."

Namaste is used as a common Hindu/Indian greeting, a salutation, a cultural sign of reverence and respect, and in some sections of India as their "good morning" greeting as well.

Origin of namaste

Ultimately (via Hindi, Punjabi, and other South Asian languages) from Sanskrit: namas te "obeisance to you" namaḥ: "homage, obeisance"
nem- in Indo-European roots te. tu- in Indo-European roots
From American Heritage Dictionary of the English Language, 5th Edition

From Sanskrit (namaste), from (námas, "bow, obeisance, reverential salutation"), and (te, "to you"), from Proto-Indo-Iranian *namas- ("to bow, prostrate"). Compare Persian (namâz).
From Wiktionary

There are a few aspects Christians should consider.

1. Namaste in Hindu culture. Though considered a part of Hindu culture, namaste has a spiritual overtone. According to Hindu belief, god is transcendent as well as immanent.

The Hindu culture is about what a person does, rather than what they believe. It is based on a universal soul or god called Brahman which takes on an ultimate number of forms that Hindus worship as gods or goddesses.

The word, Namaste comes from the more pantheistic forms of Hinduism that sees everything and everyone, in patheistic terms, as god (All is God, God is All). It is the view that god is rock, god is a tree, god is the sky or god is a squirrel, each of us is god.

In other words, it means “The divine in me bows to the divine in you,” or the “God in me bows to the God in you.”

2. Namaste and Christianity. Namaste conflicts with Christianity because the Bible teaches that humans are not gods and that humans are only to bow to the one true God, Yahweh, as well as five Bible verses forbidding bowing before angels.

* There is only one God and he does not share his glory. “I am the LORD; that is my name! I will not yield my glory to another or my praise to idols” (Isaiah 42:8).
* Bowing to or showing respect to another false god is an act of idolatry. “You shall have no other gods before me” (Exodus 20:3). Giving the namaste greeting would be like saying, “You are a god and I bow to you.”
* I, John, am the one who heard and saw these things. And when I heard and saw, I fell down to worship at the feet of the angel who showed me these things. But he *said to me, “Do not do that. I am a fellow servant of yours and of your brethren the prophets and of those who heed the words of this book. Worship God." Revelation 22:8-9
* Deepak Chopra explores the purpose of Namaste in his book, "The Spontaneous Fulfillment of Desire," emphasizing that the Sanskrit greeting Namaste (na-ma-stay) means, "I honor the divine in you" and shows the highest form of humble respect and admiration for another human being.

3. Namaste in Yoga. Namaste is used in yoga. The world of Christendom is divided on the practice of yoga.

Most Westerners consider yoga as purely the practice of physical exercise, increasing flexibility, and strengthening muscles. Their physical-only aspect of yoga is actually called "asana," and is not genuine yoga, for it fails to recognize the spiritual element on which yoga was created 4,000 years ago.

The 4,000 year old Eastern philosophy behind yoga is an ancient Hindu process to enlightenment and spiritual growth, for the word Yoga means “union” with a goal of uniting the practitioner with the Hindu god, Brahman.

Whether or not yoga is something in which Christians should participate is a question each must answer.

4. Christians and Meditation. For some Christians, yoga is an opportunity for prayer. They meet God on the mat. As they move through poses and stretches, using it as a chance for prayer and seeking God.

Namaste then becomes the practice of saying to one another, “I see you and I recognize you are a temple of the living God.” (1 Corinthians 3:16).

However, in an interview with Belief.net, Sheetal Shah, Senior Director at Hindu American Foundation disclosed this:

“Because concentration, or being present, allows us [Hindus] to focus inwards on our Divine self. We can focus on making our every thought, word, and action selfless and thus, worthy offerings to the Divine that resides in us all. But therein lies the fundamental disconnect between the teachings of yoga and [Christianity].”

The Bible teaches God’s people to meditate on God’s works and his Word, rather than on one’s inner self:

Joshua 1:8; Psalm 1:2
Psalm 63:6; Psalm 77:11-12
Psalm 143:5; Romans 12:2

The Bible teaches God’s people to worship nothing other than God:

Exodus 20:3; Exodus 34:14
Deuteronomy 6:13-14; 1 Chronicles 16:25
Psalm 96:4-5; Philippians 2:10-11
Revelation 4:8-9

Sources

Beliefnet.com, “Is "Asana" yoga Religious?”
Crosswalk.com, “Is It Okay for Christians to Practice Yoga?”
Merriam-Webster.com, “How 'Namaste' Entered The English Language.”
https://sentence.yourdictionary.com/namaste