childishness, esp. as a symptom of emotional disorder in an adult
puerilism in American English
(ˈpjuːərəˌlɪzəm, ˈpjurə-)
noun
Psychiatry
childishness in the behavior of an adult
Word origin
[1920–25; puerile + -ism]This word is first recorded in the period 1920–25. Other words that entered Englishat around the same time include: checkout, fundamentalism, montage, self-service, ski jump-ism is a suffix appearing in loanwords from Greek, where it was used to form action nounsfrom verbs (baptism). On this model, -ism is used as a productive suffix in the formation of nouns denoting action or practice,state or condition, principles, doctrines, a usage or characteristic, devotion oradherence, etc. (criticism; barbarism; Darwinism; despotism; plagiarism; realism; witticism; intellectualism)