1540s, "current in information," past-participle adjective from inform (v.). In 16c.-17c. it also could mean "unformed, formless," from in- (1) "not, opposite of," and was used in astronomy of stars that did not form part of the visual pattern of a constellation but were within it.
the informed customer
informed opinion
an informed public
informant
informatics
information
informational
informative
informed
informer
infortunate
infotainment
infra
infra-