*dheigw-

"fasten, join, attach," 1530s, from Medieval Latin affixare, frequentative of Latin affigere (past participle affixus) "fasten to, attach," from ad "to" (see ad-) + figere "to fasten" (from PIE root *dheigw- "to stick, fix").

According to OED first used by Scottish writers and thus perhaps the immediate source was French affixer, a temporarily re-Latinized spelling of Old French afichier (Modern French afficher), from a Medieval Latin variant of the Latin verb. The older form in English was affitch (Middle English afficchen, late 14c.), from Old French afichier. Related: Affixed; affixt; affixing.

"a cross or representation of a cross with the crucified figure of Christ upon in," early 13c., from Old French crucefix (12c., Modern French crucifix), from Latin cruci fixus "(one) fixed to the cross" (see crucify).