From LQWiki

The foo2bar naming convention is a naming convention for conversion programs that convert from format foo to (2) format bar.

Examples of Tools That Follow this Convention

• Addr2line
• db2html - docbook to html
• man2html
• P2P not a conversion program, but does follow the 2=to convention
• ps2pdf
• Unix2dos
• up2date also not a conversion program

This article is based, in whole or in part, on entry or entries in the Jargon File.