Decaísteis
Decaísteis is a word from the Spanish language. It is the second-person plural imperfect indicative form of the verb decaer. Decaer translates to meanings such as to decay, to decline, to fall, or to weaken. Therefore, "decaísteis" would specifically refer to the past action of "you all (plural, informal) decaying, declining, falling, or weakening."
The verb decaer is derived from the Latin word *decadere*, which also carries the meaning of falling
The imperfect tense in Spanish, used here in "decaísteis," describes an ongoing or repeated action in the