As others have said it here, it started during the neo-salafism boom in the late 2000’s, where it was the “craze” for a large segment of Somali youth.
Diaspora Muslim youth were heavy on the deen during this period to cope with the incessant Islamophobia in the media following the Iraq war. Other than the standard dawah institutions that were birthed during this period, a new flavor of salafiyah entered the scene in the UK, France, and USA fresh from Saudi Arabia and Yemen. Some disparagingly branded them Madkhalis.
Young Muslims flocked to this group due to their outward display of piety, both in lingo and dress. A lot of young Somalis in this group dropped out of higher education and the girls started wearing niqab and gloves as they completely incorporated into these mosques. It was pretty much an in-group and there was a cold war with other “madhabs” at the time.
Since there was a large and growing revert contingent who were reliant on the mosque leaders to support in getting married, the sisters in the in-group were matched with them. A lot of Arab, Pakistani, and Somali families refused to give their daughters away, but Somalis seemed the most tolerant of the bunch as evidenced by the praise that was heaped on them during sermons as the exemplary Muslim women who showed the least bias.
This praise of course turned sour as word travelled fast in this community. Expectant reverts were lining up, boldly asking for Somali girls. The sheikhs pointing to Somalis as the first stop for struggling reverts rubbed salt into the wound. Marriage horror stories started circulating the rumour mills of marriage bandits, and month old reverts marrying two/three Somali girls at the same time. This snowballed into ‘cheap and clean’. The ’one apple/reciting one surah meher‘ came from these rumours and stories too.
I believe the term itself came from America (Philly mosques as the rumours told) but was popularised in the UK - using examples from the notorious Brixton Mosque as fuel.