In Japanese, the “h” sound is often pronounced as a “b” when it occurs in the middle of a word. So they pronounce the combination of mitsu and hishi as mitsubishi.
Yataro Iwasaki (1835-1885), the founder of the old Mitsubishi organisation, decided on the three-diamond mark as the emblem for his company. The mark is said to be an arrangement of two family crests; the three-oak-leaf crest of the Yamauchi family, Lords of Tosa, where Yataro was born, and the three-tiered water chestnut crest of the Iwasaki family.
Mitsubishi companies have secured nearly 5,500 registrations for the three-diamond mark in more than 140 nations.
Info from Mitsubishi.
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