From Old Church Slavonic *письмо* (pismo), derived from *писати* (pisati, "to write"), itself from Proto-Slavic *pьsati*. Related to the Latin *pingere* ("to paint, mark") via a shared Indo-European root *peik̑-* ("to cut, mark"). The word originally referred to any writing or script before narrowing to the sense of a personal written message.

In Russian culture, letter-writing has a rich literary tradition — celebrated authors like Pushkin, Tolstoy, and Chekhov are as admired for their personal correspondence as for their fiction. The word письмо also covers email in modern usage (электронное письмо, literally "electronic letter"). Note that the closely spelled English word "plasma" or "prism" shares no relation — a common trap for false cognates when learners first encounter Cyrillic.