Its a term, I often see used. "X knife in my rotation."
I must admit, that I scoff when I encounter the term in regards to knives*
How anal/OCD would one have to be to have a 'rotation' of specific knives.
I dont collect knives (as in there is no red thread. I have an eclectic bunch ranging from vintage swords to a Dragonfly), I just have a bunch of them. Nor do I have a 'rotation' of knives.
I grab one of several off the shelf from or I use one knife for several days/weeks/months on end. In the case of the latter, that would be a kind of an EDC knife (not that I get to actually carry a knife every day).
Currently, its the Delica, which sees the most use. A great little knife.
*Beyond silly, just as the term 'deployment' for opening a knife.