the word the partner

since when the word 'the partner' becomes so commonly used?
it took me quite sometime to carefully choose a word to name my boyfriend-fiance.
i've been using it since 2007.
because from what i know,
no one else whoi know used the word 'the partner' which is why i used it to describe (my) partner.

isn't there any other word to describe your significant other?

gah!