411 REFERENCE · Wiktionary
-tse
Reference material by Wiktionary contributors. This retains its source identity and is not 411 news reporting.
Appendix:Variations of "tse"
Finnish
Suffix
adverb
fi -itse
Usage notes
Although commonly analysed synchronically as fi -tse added onto the plural stem of the word, in origin the suffix simply began with fi -i- (like fi -inen), and no plural stem was involved.