late 14c., "steadfast, resolute," from Old French constant (14c.) or directly from Latin constantem (nominative constans) "standing firm, stable, steadfast, faithful," present participle of constare, from com- "together" (see com-) + stare "to stand," from PIE root *sta- "to stand" (see stet). Of actions and conditions from 1650s. Related: Constantly.
1832 in mathematics and physics, from constant (adj.).
constant con·stant (kŏn'stənt)
Continually occurring; persistent.
Unchanging in nature, value, or extent; invariable.
A quantity assumed to have a fixed value in a specified mathematical context.
An experimental or theoretical condition, factor, or quantity that does not vary or that is regarded as invariant in specified circumstances.