This word is from the Spanish tocino.
Also spelled tusino or tucino. The trend these days is to adhere to the original Spanish spelling.
The Filipino-style cured meat tosino is often compared to bacon, even ham. The meat used is most often pork, though beef and chicken are common as well. The mixture used in curing includes salt, sugar, water and annatto.
A common way to serve tosino is as tosilog (with fried rice and fried eggs on a single plate).
Please don’t buy the Pampanga’s Best or Magnolia brand of tocino in the United States. Both (yes, even the Magnolia brand with the iconic Magnolia logo) were pirated from the Philippines by an American company.
You read right: those Pampanga’s Best and Magnolia products you see in the USA are NOT in any way related to what real Filipinos grew up with. It’s an infamous case of brand piracy and trademark squatting known to the Filipino-Americans as the OMGpeke scandal.
Traditionally, salitre (saltpeter) was one of the ingredients used in making Filipino tocino. Today at Filipino grocery stores, you can buy tocino-marinating mixes that proudly declare on the label: Walang Salitre (No Saltpeter).