assignation (n.) Look up assignation at Dictionary.com
early 14c., "appointment by authority," from Old French assignacion (14c., Modern French assignation), from Latin assignationem (nominative assignatio) "an assigning, allotment," noun of action from past participle stem of assignare/adsignare "to mark out, to allot by sign, assign, award," from ad "to" (see ad-) + signare "make a sign," from signum "mark" (see sign (v.)).

Meaning "action of legally transferring" (a right or property) is from 1570s; that of "a meeting by arrangement, tryst" is from 1650s, especially for a love-affair; assignation-house (1849) was an old euphemism for "brothel."