The story
From baker's dozen (“thirteen, one more than a dozen”) by analogy, hence “seven, one more than a half dozen”.
Etymology from Wiktionary, CC BY-SA 4.0.
baker's half dozen
Today it means: Seven, a group of seven. Full definition →
Today it means: Seven, a group of seven. Full definition →
From baker's dozen (“thirteen, one more than a dozen”) by analogy, hence “seven, one more than a half dozen”.
Etymology from Wiktionary, CC BY-SA 4.0.