Where does “safety valve” come from?

safety valve (English) comes from English safety, from Middle English savete, from Old French sauveté, from Medieval Latin salvitas, from Latin salvus, from Proto-Italic *salawos, from Proto-Indo-European solh₂wós, from Proto-Indo-European sōlh₂- — mercy, comfort; comfort, mercy.

safety valve (English): A valve set to open at a pressure below that at which a container holding a gas, vapour, etc. (such as a boiler or pressure cooker), would burst, thus reducing the pressure; a relief valve

Definitions

  1. A valve set to open at a pressure below that at which a container holding a gas, vapour, etc. (such as a boiler or pressure cooker), would burst, thus reducing the pressure; a relief valve

Ancestry of “safety valve”, step by step

safety valve traces back through two separate lines of ancestry.

via English safety

StepLanguageWordMeaning
1EnglishsafetyThe condition or feeling of being safe; security;...
2Middle EnglishsaveteSafety, security; being unharmed or unharmable
3Old Frenchsauveté
4Medieval Latinsalvitas
5Latinsalvussafe, saved, preserved, sound, unharmed,...
6Proto-Italic*salawoswhole
7Proto-Indo-Europeansolh₂wós
8Proto-Indo-Europeansōlh₂-mercy, comfort; comfort, mercy

via English valve

StepLanguageWordMeaning
1EnglishvalveA device that controls the flow of a gas or fluid...
2Latinvalvadouble or folding door; one leaf of such doors
3Proto-Italic*wolVwā-
4Proto-Indo-European*wol-ew-o-
Every word from Proto-Indo-European sōlh₂-