Why is the ninth month called September?
mid-15c., "communication to and fro," from Old French entrecours "exchange, commerce," from Late Latin intercursus "a running between, intervention," from intercursus, past participle of intercurrere "to run between," from Latin inter- "between" (see inter-) + currere "to run" (see current (adj.)). Meaning "sexual relations" first recorded 1798, from earlier sense "social contact and relations" (1540s).
intercourse in·ter·course (ĭn'tər-kôrs')
Dealings or communications that occur between persons or groups.