Unimportant means not mattering much. An unimportant detail, relatively unimportant, unimportant in itself.
It is a judgement about weight rather than truth: an unimportant fact can be perfectly accurate. Relatively unimportant is the standard hedge, since almost nothing is unimportant in every context. Note that calling somebody's concern unimportant is a reliable way of making it important; and that unimportant is one of the plainest un- words in the language.
1adjectiveunimportantNot mattering much.
“Don't worry about the unimportant details; focus on the main idea.”
unimportant is a quality of insignificance.
Medieval Latin
importāns
Middle English
important
English
important
English, today
unimportant
From un- + important. important comes from Middle English important, from Medieval Latin importāns. by surface analysis, import + -ant. Displaced native Old English hēah and hefiġ.
Etymology from Wiktionary, CC BY-SA