'reliably-guided' originates from Modern English, specifically the adverb 'reliably' and the past participle 'guided', where 'reliably' meant 'in a reliable manner' and 'guided' meant 'led or directed'.

'reliably' developed from the adjective 'reliable' (formed from the verb 'rely' + suffix '-able') and the adverbial suffix '-ly'; 'rely' is attested in Middle English via Old French. 'guided' is the past participle of 'guide', a word borrowed into English from Old French 'guider'.

Initially the elements meant separately 'in a reliable way' and 'led'; over time the compound came to be used as a single descriptive adjective meaning 'led in a reliably consistent manner'.