Jean Leurechon

Jean Leurechon (c. 1591 – 17 January 1670) was a French Jesuit priest, astronomer, and mathematician, known for inventing the pigeonhole principle and naming the thermometer.

[3] Leurechon taught mathematics from 1614 to 1629 at Pont-à-Mousson,[4] and in 1631 became rector of the Collège Gilles de Trèves [fr], a Jesuit school in Bar-le-Duc.

[7] In 1622 he published the book Selectæ Propositiones in Tota Sparsim Mathematica Pulcherrimæ.

It has been commonly attributed to Leurechon, and the van Etten name interpreted either as a pseudonym or as a "modest" misattribution, but this has been disputed by some scholars, who argue that an actual student named van Etten was the author.

[5] The 1622 book contained a brief reference to the pigeonhole principle, much earlier than its common attribution to Peter Gustav Lejeune Dirichlet in 1834, and the 1624 book spelled out the principle in more detail.