"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.
1901, slang, "the penis," also "the female pudendum." The slang meaning "extraordinary person or thing" is by 1943, now usually meaning an extraordinarily distasteful or unpleasant person or thing.
Latin, literally "wonderful to relate," from neuter of mirabilis "wonderful, marvelous, extraordinary; strange, singular" (see marvel (n.)) + ablative supine of dicere "to say, speak" (from PIE root *deik- "to show," also "pronounce solemnly"). The expression is found in Virgil. Mirable "wonderful, marvelous" was used in English 15c.