Readily availavble knowledge. As in "I don't know off hand."
An offhand remark is a remark that is spoken without thought. Similar to something blurted out.
Offhand; without previous study; extemporaneous; extempore; as, an impromptu verse., Something made or done offhand, at the moment, or without previous study; an extemporaneous composition, address, or remark., A piece composed or played at first thought; a composition in the style of an extempore piece.
Offhand is the odd term because it has nothing to do with unplanned actions.
If you mean towns and cities named Springfield, probably quite a few. I know three offhand - MA, IL, and OH.
That is not a phrase
what does the phrase rule of thumb mean
what does the phrase There`s ruin in store for you mean
a phrase that is traditional
"Grave" is a phrase that can mean serious.
offhand
offhand, I'd throw out coloration
"The phrase 'mean slow toffee' does not have a commonly recognized meaning. It may be a colloquial expression or a phrase that is not widely known."