Sincerity

google

ref

mid 16th century (also in the sense ‘not falsified, unadulterated’): from Latin sincerus ‘clean, pure’.

wiktionary

ref

From Middle English sinceritie, from Old French sincerité and Medieval Latin sincēritas; both from Latin sincēritas, from sincērus + -tās. Equivalent to sincere +‎ -ity.

etymonline

ref

sincerity (n.)

early 15c., sincerite, "honesty, genuineness," from Old French sinceritie (early 16c., Modern French sincérité) and directly from Latin sinceritatem (nominative sinceritas) "purity, soundness, wholeness," from sincerus "whole, clean, uninjured," figuratively "sound, genuine, pure, true, candid, truthful" (see sincere).