the word 'undecided' is a relatively modern english formation, built upon the older verb 'decide'. the core verb 'decide' originates from the latin decidere, meaning "to cut off" or "to settle", which itself is composed of de- ("off") and caedere ("to cut"). this metaphor of cutting off alternatives to reach a conclusion evolved into the modern sense of making a choice. the old english negative prefix 'un-' was attached to the past participle 'decided' to create an adjective describing a state where a conclusive cut or choice has not yet been made. the '-ed' suffix here functions adjectivally, indicating the possessed quality of being unresolved.

Structure: un (not) + decide (to make a choice) + ed (adjective suffix) un- (old english, a prefix expressing negation); decide (from latin decidere, meaning "to cut off, determine"); -ed (old english, a suffix forming adjectives from verbs or nouns, indicating a state or condition).