extra

word-forming element meaning "outside; beyond the scope of; in addition to what is usual or expected," in classical Latin recorded only in extraordinarius, but more used in Medieval Latin and modern formations; it represents Latin extra (adv.) "on the outside, without, except," the old fem. ablative singular of exterus "outward, outside," comparative of ex "out of" (see ex-).

"being beyond or out of the common order or rule; not of the usual, customary, or regular kind," early 15c., from Latin extraordinarius "out of the common order," from extra ordinem "out of order," especially the usual order, from extra "out" (see extra-) + ordinem, accusative of ordo "row, rank, series, arrangement" (see order (n.)).

Of officials, etc., "outside of or in addition to the regular staff," often "temporarily employed for a specific purpose," from 1580s. Also from 1580s in the sense of "remarkable, uncommon, rare, wonderful." Related: Extraordinarily; extraordinariness.