The word 'surrogacy' is built upon the Latin verb 'surrogare', a variant of 'subrogare', which combines 'sub-' (under, in place of) and 'rogare' (to ask, propose). In Roman law, this term described the act of putting one person in the place of another, such as appointing a substitute. Over centuries, the core concept of substitution was retained as the word evolved through French influence into English 'surrogate', meaning a deputy or replacement. The modern abstract noun 'surrogacy', formed by adding the suffix '-acy', specifically denotes the state or arrangement of acting as a substitute, most prominently in the context of bearing a child for another.

Structure: surrog (substitute) + acy (state or condition) - 'surrog' originates from Latin 'subrogare/surrogare', meaning 'to substitute, put in another's place'. Its functional role is the core root conveying the concept of substitution. - 'acy' is a noun-forming suffix of Latin origin (via French '-acie'), indicating a state, condition, or quality.