1
general::
Act on one's own authority without permission from another, as in I took the liberty of forwarding the mail to his summer address. It is Also put as take the liberty to, as in He took the liberty to address the Governor by her first name. This rather formal locution was first recorded in 1625 and does not imply the opprobrium of the similar-sounding TAKE LIBERTIES.
American Heritage Idioms
2
general::
Phrase(s): take the liberty of doing something
to do something for someone voluntarily; to do something slightly personal for someone that would be more appropriate if one knew the person better. (Often used as an overly polite exaggeration in a request.) • Do you mind if I take the liberty of flicking a bit of lint off your collar? • May I take the liberty of removing your coat? • I took the liberty of ordering an entree for you. I hope you don’t mind.
McGrawhill's American Idioms And Phrasal Verbs