Its the abbreviation for "Buy one, Get one at Half off."
Used to replace the overly misused advertising slogan "Buy one, Get one" since no one is offering that anymore.
Now she has to buy TWO pairs at full price to get the third pair for half."
Its not BOGO anymore, its BOGOHO.
This comes from BOGOHO, Buy One Get One Half Off. It's very disappointing when something is represented as BOGO when it's actually BOGOHO.