käyttämiesi
The Finnish word "käyttämiesi" is a possessive form of the past active participle of the verb "käyttää," which means "to use." Specifically, it translates to "those you used" or "the ones you used." This form indicates that the speaker is referring to something plural that the listener or reader previously employed.
"Käyttämiesi" is constructed by taking the past active participle "käyttämä" (used) and adding the plural possessive
For example, in the sentence "Mitä olivat käyttämiesi kirjat?" the translation would be "What were the books