Why is the ninth month called September?
c.1600, perhaps from French filtration (1570s), noun of action from filter "to filter" (see filter (v.)).
filtrate fil·trate (fĭl'trāt')
v. fil·trat·ed, fil·trat·ing, fil·trates
To put or go through a filter. n.
Material, especially liquid, that has passed through a filter.
filtration fil·tra·tion (fĭl-trā'shən)
The process of passing a liquid through a filter.