Why is the ninth month called September?
1570s, originally in rhetoric, from Late Latin metastasis "transition," from Greek metastasis "a removing, removal; migration; a changing; change, revolution," from methistanai "to remove, change," from meta- "over, across" (see meta-) + histanai "to place, cause to stand," from PIE root *sta- "to stand" (see stet). A rhetorical term in Late Latin for "a sudden transition in subjects," medical use for "shift of disease from one part of the body to another" dates from 1660s in English. Related: Metastatic.
metastasis me·tas·ta·sis (mə-tās'tə-sĭs)
n. pl. me·tas·ta·ses (-sēz')
Transmission of pathogenic microorganisms or cancerous cells from an original site to one or more sites elsewhere in the body, usually by way of the blood vessels or lymphatics.
A secondary cancerous growth formed by transmission of cancerous cells from a primary growth located elsewhere in the body.