How is "按揭" a Cantonese loanword of Mortgage from English?
Wiktionary [1] claims that among the explanations, none claims that 按 is a transcription for mort-. Seemingly there is a version that the original first character was 摸 /mo2/, which makes more sense, and it was replaced by 按 by meaning.

/mo2kit3/ is a MUCH better match than /on3kit3/, and with what other final could English [gɪdʒ] be approximated, if Cantonese allows only -p, -t, -k outside of nasals? [t̚] and [dʒ] are both approximately dental as opposed to labial or velar, and, as any Korean would confirm, when finally unreleased [tɕ~dʑ] defaults to [t̚], so transcription appears flawless. As soon as English card goes to /kaat1/ [2], the behaviour of [dʒ]should not be surprising.

References:

[1] https://en.wiktionary.org/wiki/%E6%8C%89%E6%8F%AD

[2] https://wenlin.co/wow/Special:Wenlin/QQs%3Fs%3Dkaat1