The term 'Mother Lodge' (meaning the lodge in which you were Initiated) is almost an official term in the GL of Scotland. It appears in the EA Obligation in the ritual used by my 'Mother Lodge'. Grand Lodge itself refers to the lodges under it as 'daughter lodges' in 'The Constitution and Laws'. My lodge would refer to other lodges in the area as 'sister lodges'. We refer to the Grand Lodge of Newfoundland and Labrador as our 'sister constitution' or 'sister jurisdiction'. The first lodge on the Roll of the GL of Scotland, Lodge Killwinning No. O, (yes 'zero!) is often referred to as 'Mother Killwinning' as at one time it chartered 'daughter lodges'. The custom of referring to freemasonry as somehow 'feminine' is very old indeed. As to WHY it is so - like a lot in freemasonry, it is just 'because it always has been'!