But why "Install-Package", "Add-Package" and "Update-Package" - it's not like you can install, add or update anything else with this tool.
Long story short: These are "Commandlets", commands provided to your PowerShell-session through extension-modules.
The PowerShell convention for command-names are Verb-Noun, like for instance Get-DiskImage or whatever, so it makes sense that OneGet builds on these.