The Spanish word 'miga' comes from the Latin word 'mica', which meant 'crumb, morsel, or small particle'. The meaning has remained remarkably stable over time, as 'miga' in Spanish specifically refers to a bread crumb or the soft part of bread. The change from Latin 'mica' to Spanish 'miga' shows a common sound change pattern in the development from Latin to Spanish, where the 'c' sound became voiced to a 'g' between vowels.

A common related Spanish word is 'migaja', which is a diminutive form of 'miga' and means 'tiny crumb' or 'little bit'. You might also encounter 'migas', the plural form, which is a popular Spanish dish made with bread crumbs and other ingredients.

While not directly related to 'miga', English speakers might find it interesting that the word 'mica' in English (the mineral that can be split into very thin sheets) comes from the same Latin root 'mica'. This connection makes sense when you consider that both bread crumbs and the mineral can be broken down into small particles.