Excogitation means 'the act of thinking or studying intensely',
and hence 'the result of thinking; a contrivance'."
Excogitation is from excogitate
'to think out; devise; study intensely',
derived ultimately from Latin excogitare.
It is first found in English in the early sixteenth century.
the ardour of enquiry will sometimes give way to idleness or satiety"
(Samuel Johnson, Rasselas).
"To the excogitation of this problem,
he had devoted many anxious hours"
(Dickens, Our Mutual Friend).