Bucky often hearkened back to some popular tune of his day, when explaining his effectiveness (way beyond just moralizing, pronouncing judgments), his craft, involving trim-tabbing and such.
Inventiveness within language, coming up with a deliberately remote vocabulary, was a big part of it for him. While he (sometimes quietly) conceded when the competition had bested him, he at least kept a few words for himself: like spin.
What Bucky meant by "spin" is closer to what is today meant by "spin doctor" i.e. someone who imparts meaning in some sly and precessional way (that's Bucky's meaning of precessional).
Or maybe it just looks sly (crooked, weird) to more straight-ahead types. But for Bucky it was "deliberately non-straight" and in that sense perfectly natural (how nature does business).