Thermometer

google

ref

mid 17th century: from French thermomètre or modern Latin thermometrum, from thermo- ‘of heat’ + -metrum ‘measure’.

wiktionary

ref

Borrowed from French thermomètre, equivalent to thermo- +‎ -meter.

etymonline

ref

thermometer (n.)

1630s, from French thermomètre (1620s), coined by Jesuit Father Jean Leuréchon from Greek thermos "hot" (see thermal) + metron "measure" (from PIE root *me- (2) "to measure"). An earlier, Latinate form was thermoscopium (1610s). The earliest such device was Galileo's air-thermometer, invented c. 1597. The typical modern version, with mercury in glass, was invented by Fahrenheit in 1714. Related: Thermometric; thermometrical.