Mike Marcus replies:
Curtal as a noun is not uncommon in early modern literature (as VN knew), when horses were ubiquitous. Shakespeare uses it in All's Well, and in Chapman's 'Gentleman Usher' the word occurs three times in the first few lines of the play, in Poggio's dream.
Incidentally, bow-leggedness is also a typical theme in early modern comedy. It was characteristic of venereal disease, the "French pox", such that the sufferer walked "tressel-legged" (as toward the end of Chapman's 'Widow's Tears').
The color gray (VN's "gray car" and "grayness") also seemed to have some symbolic significance for early modern writers (Shakespeare & Jonson especially) but I don't know what it was.
MM