Music origin

'Do re mi fa so la ti' is the English version of the Tonic Sol-Fa system invented (or rather adapted from the Continental 'solfege' system, which has 'sol' and 'si' rather than 'so' and 'ti') by John Curwen in the 19th C. In fact the earliest version of a letter notation seems to have been 'Ut re mi fa sol la' (with no leading note or 7th). The Tonic Sol-fa system is not intended to be key-specific: 'do' represents the tonic and can be any pitch (usually specified in music published in this notation) and the scale is normally the major scale. Accidentals are represented by changing the vowel. The use of the letters A - G was originally another pitch independent system with A being the tonic of the (then more common) Ionian mode, which is now known as the 'natural minor' scale (represented by playing all the white notes on a keyboard starting with A as the tonic). Since these note names became fixed to certain pitches, usage has changed to consider the major diatonic scale (or Ionian mode) as 'normal', so the Ionian scale starting with C as the tonic has become the customary 'home' key with the intermediate semitones being regarded as 'accidentals' and only fixed in pitch on keyboard instruments. In vocal music and on an instrument where pitch is infinitely variable, such as a violin, there is an actual difference between, for example, G# and Ab. I am not sure how the pitch of A = approximately 440Hz came to be fixed as such. I imagine that that was approximately the pitch which most male voices consider as 'mid range' (since the most influential people in early music were monks). I can't find any satisfactory explanation for the 'ut re mi fa sol la si' sequence either but I have heard that the names come from the first syllables of a well-known Latin anthem which happened to use the whole diatonic scale as its melody.

I believe it's the European / Latin music system. In other cultures they split semitones etc into many smaller parts.

With great respect for the answer above, it's really a simple matter of tradition. Why do we call anything what we call it? Why not?