My Cebuana wife says sinso is a chainsaw although she is not aware of the spelling. Neither this dictionary nor Google Translate knows it, though.

It's probably the nativized form of "chainsaw"

We can see the phonology from chainsaw to sinsu:

Let's get their IPA forms first (for Chainsaw, I'll be using the US IPA):

Chainsaw -> [ˈt͡ʃeɪnˌsɔ]
Sinsu -> [ˈsiːnˌsʊ]

Vowel Changes:

  • the diphthong [eɪ] is approximated as [ɪː] in Cebuano.
  • the vowel [ɔ] is approximated as [ʊ] in Cebuano.

Consonant Changes:

  • the consonant [t͡ʃ] is approximated as [s] in Cebuano.

Applying what we got:

  • Applying the vowel changes: [ˈt͡ʃeɪnˌsɔ] -> [ˈt͡ʃɪnˌsʊ]
  • Applying the consonant changes: [ˈt͡ʃɪnˌsʊ] -> [ˈsiːnˌsʊ]

And thus, sinsu comes from chainsaw