Airle-Penny

This word is of remote antiquity and refers to an ancient custom of giving arrhoe, or presents, from a man to a woman on their entering into a contract to marry. The present was generally an annulus, or ring, and in reference to the sanctity of the engagement the gift was subsequently called a God's pennie. Though in its primary signification it imported a spousal gift, the lapse of time has converted the use of the word to earnest money given to bind any bargain.

- William Toone's Etymological Dictionary of Obsolete Words, 1832

Arle, money given in confirmation of a bargain . . . when a servant is hired.

- Sir James Murray's New English Dictionary, 1888