overoptimistic

Etymology tree
Proto-Indo-European *úp
Proto-Indo-European *-er
Proto-Indo-European *upér
Proto-Germanic *uber
Old English ofer-
Middle English over-
English over-
Proto-Indo-European *h₁ep-der.
Proto-Indo-European *h₁épsder.
Proto-Indo-European *h₁epi
Proto-Indo-European *-tm̥mos
?
Latin optimus
Proto-Indo-European *-id-
Proto-Indo-European *-yéti
Proto-Indo-European *-idyéti
Proto-Hellenic *-íďďō
Ancient Greek -ῐ́ζω (-ĭ́zō)
Proto-Indo-European *-mos
Proto-Indo-European *-mós
Ancient Greek -μός (-mós)
Ancient Greek -ῐσμός (-ĭsmós)der.
Latin -ismusbor.
French -isme
French optim(isme)
▲
Ancient Greek -ῐ́ζω (-ĭ́zō)
Proto-Hellenic *-tās
Ancient Greek -τής (-tḗs)
Ancient Greek -ῐστής (-ĭstḗs)bor.
Latin -istabor.
French -iste
French optimistebor.
English optimist
Proto-Indo-European *-ikos
Proto-Italic *-ikos
Latin -icuslbor.
Old French -iquebor.
Middle English -ik
English -ic
English optimistic
English overoptimistic
From over- + optimistic.