In Vedic Sanskrit:

• Brahma (ब्रह्म) (nominative singular), brahman (ब्रह्मन्) (stem) (neuter gender) from root bṛh-, means "to be or make firm, strong, solid, expand, promote".
• Brahmana (ब्रह्मन) (nominative singular, never plural), from stems brha (to make firm, strong, expand) + Sanskrit -man- from the Indo-European root -men- which denotes some manifest form of "definite power, inherent firmness, supporting or fundamental principle"
• Brahman is a concept present in Vedic Samhitas, the oldest layer of the Vedas dated to the 2nd millennium BCE. For example,

  The Ṛcs are limited (parimita),
  The Samans are limited,
  And the Yajuses are limited,
  But of the Word Brahman, there is no end.

  — Taittiriya Samhita VII.3.1.4, Translated by Barbara Holdrege