'pier' originates from Middle English, borrowed from Old French (such as 'piere' or similar forms), ultimately related to words meaning 'stone' (connected with Latin 'petra' via Romance languages).

'pier' changed from Old French forms into Middle English (appearing as 'peer'/'pier') and eventually became the modern English word 'pier' with senses for a projecting platform and for an architectural support.

Initially associated with the idea of a stone or solid support, over time it evolved into the current senses of 'a structure projecting into water for boats/recreation' and 'a vertical supporting element in architecture'.