'ill-guided' is a compound of the prefix 'ill-' (from Old English 'yfel' meaning 'bad') and 'guided', the past participle of 'guide' (from Old French 'guider', meaning 'to lead or show the way').

'guide' entered Middle English as 'guīden' via Old French 'guider' and developed into modern 'guide'; the prefix 'ill-' was used in Late Middle English to form compounds meaning 'badly' + past participle, producing forms such as 'ill-guided'.

Initially it meant 'badly led or directed'; over time the term has retained that basic sense but is also used figuratively to mean 'poorly advised' or 'misinformed'.