Reconstruction:Proto-Finnic/-ait'ak

Probably a variant of *-it'ak with rebracketing/re-extraction from a-stems into the suffix. The lack of the standard labialization *-ai- > *-oi- suggests a relatively recent origin or prevention of the sound change by analogy.

Holopainen & Junttila (2022) propose that the entire *-aida- suffix may have originally come about as a result of rebracketing applied to verbs borrowed from Baltic (with metathesis *-ja- > *-ai-) and suffixed with *-ta- (e.g. Baltic *tempja > Finnic *tëmpai-da- > *tëmp-aida-).^[1]

*-ait'ak / *-äit'äk (stem *-aida- / *-äidä-)

1. Forms verbs, often continuative or frequentative, mainly from nominal stems.

• This suffix was particularly productive in onomatopoeic stems, especially in later eastern varieties of Northern Finnic (Eastern Finnish, Karelian, Veps and intermediate varieties), but some examples can be reconstructed back to Proto-Finnic, such as *heläit'äk, *kumait'ak and (possibly) *hauk'ait'ak, *rabait'ak.
• With regard to Indo-European borrowings, many verbs (mostly Baltic; also some Germanic, but see *-it'ak) have been assimilated with this suffix.

• *heläit'äk
• *kumait'ak
• ? *hauk'ait'ak
• ? *rabait'ak

• Finnish: -ajaa (dialectal, stem -aja-, e.g. heläjää, kumajaa)
• Veps: -aita