våffeldag

Compound of våffla (“waffle”) +‎ dag (“day”). A jocular folk etymological transition from vårfrudagen (“Lady Day”). According to SAOB attested since 1888.

våffeldag c

1. (chiefly in the definite) waffle day, Lady Day; a day when waffles are traditionally eaten
   • 28 Mar 1879, “Krönika.”, in Vesternorrlands Allehanda.‎:

     "Våffeldagen" i tisdags var likasom en försmak af det stora, veckolånga skollof, hvilket i alla rättänkande skolgossar och skolflickors (vi hade så när sagdt äfven skollärares) ögon utgör den förnämsta epoken i hvarje vårtermin.

     "Waffle Day" last Tuesday was like a foretaste of the large, week-long school holiday, which in the eyes of all right-thinking schoolboys and schoolgirls (and we on the brim nearly included schoolteachers) constitutes the most important epoch in each spring term.

   Synonym: vårfrudag (“Lady Day”)

In Sweden celebrated on March 25th. Also coincidences with the otherwise unrelated trandagen (“crane day”) in many areas.

• våffeldag in Svensk ordbok (SO)
• våffeldag in Svenska Akademiens ordbok (SAOB)