'steadily-controlled' originates from modern English as a compound of 'steadily' and 'controlled', where 'steadily' is formed from 'steady' + the adverbial suffix '-ly' and 'controlled' is the past participle form of the verb 'control'.

'steady' comes from Old English 'stædig' / 'staedig' meaning 'firm, stable'; 'steadily' developed by adding the adverbial suffix '-ly'. 'control' entered English via Old French/Middle English from Medieval Latin 'contrarotulare' (to check against a roll), evolving into Middle French 'controler'/'contreroller' and then English 'control', with 'controlled' as its past participle.

Individually, 'steady' originally meant 'firm or fixed (place/position)', and 'control' originally meant 'to check or verify against a roll'; over time they evolved so that combined uses convey the modern sense of 'kept under even regulation'—a current meaning of 'steadily-controlled'.