'realistically-guided' is a modern compound formed from the adverb 'realistically' (from 'realistic' + suffix '-ally') and the past-participial adjective 'guided' (from the verb 'guide'). 'realistic' ultimately derives from French 'réaliste' and Modern Latin elements from Latin 'realis' meaning 'real'. 'guide' originates from Old French 'guider' meaning 'to lead or direct', from a Germanic source.

'realistically-guided' developed from the two-word descriptive phrase 'realistically guided' into a hyphenated compound as contemporary English increasingly uses hyphenation to mark close adjectival units before nouns.

Initially the phrase simply described something 'guided in a realistic manner'; over time the hyphenated compound has come to function as a single adjectival unit emphasizing method or orientation (i.e., 'realism as the guiding principle').