forviŝi

Forviŝi decodes cleanly, and decoding it is the point of meeting it here. It is for, the word meaning "away" doing duty as a prefix, on the root viŝ-, "to wipe". Wipe plus away: wipe away, erase, and by an easy extension delete a file. Viŝi on its own is the plain act - viŝi la tablon, wipe the table - and it arrives later than this page, at rank 2518 in chapter 27. That is worth stating rather than hiding: you met the compound before the base, which happens whenever the compound is the commoner word in print.

The prefix is doing real work. For is a full adverb in its own right (iru for - go away), and Esperanto lets you weld it to the front of a verb to add the sense of removal: forpreni take away, fordoni give away, forĵeti throw away, forviŝi wipe away. Once you see the pattern, half a dozen verbs come free.

For the computing sense there is competition. Forigi (rank 737) is the neutral "remove, delete" and is what most software interfaces use. Forviŝi is the more physical, more final-sounding one - you can hear the cloth in it - which is exactly why it turns up for wiping a disk or erasing a memory.