English
indeterminably
From in- + determine + -ably.
Formed from in + determine + ably
Proto-Indo-European *h₁én ‘in’
Proto-Germanic *in
Proto-West Germanic *in
Old English in
Middle English in ‘inside’
English in
Proto-Indo-European *térmn̥ ‘boundary’
…
Latin terminō ‘to set bounds to, limit’
Latin dēterminō ‘to delimit, set bounds to’
Old French determiner
Middle English determinen
English determine
Middle English abeliche
English ably
Today it means
adv in an indeterminable manner
Language periods are conventional ranges, not dates for this word.
Etymograph / indeterminably