'antihectic' originates from Greek and New Latin elements: the prefix 'anti-' (from Greek 'anti' meaning 'against') combined with 'hectic' (from New Latin 'hecticus' ultimately from Greek 'hektikos').

'hectic' passed into English from New Latin 'hecticus' (via French/Medieval Latin), derived from Greek 'hektikos' (relating to habit or habitual fever). The English formation 'antihectic' appeared in post-medieval medical and literary usage by attaching the prefix 'anti-' to 'hectic' to mean 'against hectic (fever)'.

Initially, the term was used in medical contexts to mean 'opposed to hectic fever' (i.e., reducing feverish symptoms). Over time it also gained a broader, figurative sense of 'not hectic; calm' though the word remains rare and often marked archaic in medical usage.