What is the meaning of -tt?

past-tense and past-participle suffix (homonymous form in the vast majority of verbs):

  1. -ed, -t (forms the past tense of a verb)

    -ed, -t (forms the past tense of a verb)

    -ed, -t (forms the past participle of a verb)

    Added to a noun or an adjective to form the locative case.

    Source: wiktionary.org