to boot

From Middle English to bote (“something added to, addition”), from Old English tō bōte (“to boot, besides, moreover”). See boot (“profit, gain, remedy”).

to boot (not comparable)

(idiomatic, informal) In addition, besides, also.
My boyfriend is funny, and a pretty good cook to boot.
- 1606, Caius [i.e., Gaius] Suetonius Tranquillus, “The Historie of Caius Iulius Cesar Dictator”, in Philêmon Holland, transl., The Historie of Twelve Cæsars Emperours of Rome. […], London: […] [Humphrey Lownes and George Snowdon] for Matthew Lownes, →OCLC, section 38, page 16:
  Among the people (of Rome) beſide x. modij of corne, & as many pints of oyle, he diſtributed & dealt 300 Seſterces alſo by the poll, vvhich hee had in times paſt promiſed, vvith an overdeale of 100. a peece to boote, for time.

Almost always placed in clause-final position; compare on top of that.

in addition — see in addition

in addition, besides, also