Old name rejected.

Black Flat? Let's ask someone who lives there and has taken that original title as their strangely appropriate business name:

Black Flat Coffee Brewers was named after "Black Flat", the original name of Glen Waverley before it was renamed in 1921. Originally developed as orchards and farming lands, Black Flat ... was in reference to the dark, rich soil and flat ground.

Being precisely descriptive, the original name makes Glen Waverley - a name doubly adopted from a Sir Walter Scott novel via Edinburgh - seem a little pretentious. Perhaps that is why the suburb within a few decades became synonymous with the somewhat pretentious 'Sherry Belt', a sardonic Barry Humphries reference to 1960s stay-at-home upper middle class wives who, bored, took to entertaining their guests with sherry parties.