Early 19th century; earliest use found in John Mactaggart (1791–1830), engineer and poet. Probably originally a (probably euphemistic) alteration of Lord defend thee or a similar phrase, but perhaps influenced in form by association with Scots lockanties, perhaps itself an alteration of lack-a-day. A number of shortened forms of the interjection are also found, perhaps showing some influence from the English regional (northern) interjections lauves-me, loavins, etc.; longer forms in English regional (northern) use such as loavena-days or lofin-days may perhaps also have influenced the Scots exclamation.