Other forms: overthinking, overthought
To overthink is to think about something so much that you make it worse. Overthink the decision, stop overthinking, overthink it.
The finding behind the word is real: for some decisions, deliberating longer produces worse choices, because attention shifts to features that are easy to describe rather than the ones that matter. It is also what keeps people awake. Note that the Old English verb meant simply to think over.
1verboverthinkTo think about something so much that you make it worse.
“Don't overthink it; just pick the one you like best.”
overthink is an excessive thinking.
Over plus think, from Old English oferthencan, to think over. The critical sense is modern.
Middle English
thinken
English
think
English, today
overthink
From over- + think. think comes from Middle English thinken. From Middle English thinken, thynken, thenken, thenchen, from Old English þenċan, from Proto-West Germanic þankijan, from Proto-Germanic þankijaną (“to think”), from Proto-Indo-European teng- (“to think, feel, know”). Cognate with Scots think, thynk (“to think”), frr teenk, taanke, tanke, tånke (“to think”), stq toanke (“to think”), West Frisian tinke (“to think”), Dutch denken, dinken (“to think”), Afrikaans dink (“to think”), Low German denken, dinken (“to think”), German denken (“to think”), Danish tænke (“to think”), Swedish tänka (“to think”), Norwegian Bokmål tenke (“to think”), Norwegian Nynorsk tenkja (“to think”), Icelandic þekkja (“to know, recognise, identify, perceive”), Gothic þagkjan (“to think”), Latin tongeō (“know”).
Etymology from Wiktionary, CC BY-SA