"one of no faith or religion," 1560s, from Latin nulli-, combining form of nullus "no" (see null) + fides "faith" (from PIE root *bheidh- "to trust, confide, persuade"). As an adjective from 1620s.
Entries linking to nullifidian
null adj.
"void of legal force, invalid," 1560s, from French nul, from Latin nullus "not any, none," from ne- "not, no" (from PIE root *ne- "not") + illus "any," diminutive of unus "one" (from PIE root *oi-no- "one, unique").
*bheidh-
Proto-Indo-European root meaning "to trust, confide, persuade."
It forms all or part of: abide; abode; affiance; affidavit; auto-da-fe; bide; bona fide; confederate; confidant; confide; confidence; confident; defiance; defy; diffidence; diffident; faith; fealty; federal; federate; federation; fiancee; fideism; fidelity; fiducial; fiduciary; infidel; infidelity; nullifidian; perfidy; solifidian.
It is the hypothetical source of/evidence for its existence is provided by: Greek pistis "faith, confidence, honesty;" Latin fides "trust, faith, confidence, reliance, credence, belief;" Albanian be "oath," bindem "to be convinced, believe;" Old Church Slavonic beda "distress, necessity," bediti "to force, persuade;" Old English biddan "to ask, beg, pray," German bitten "to ask."