Lycoming, a corruption of the Lenape word for “sandy stream”, originated as a Pennsylvania creek; that state’s Lycoming County was founded around the creek in 1795. How did the name make its way to Diamond Bar? Most likely because of a phone number. From the 1920s to the 1960s, the AT&T monopoly, a.k.a. the Bell System, employed a mnemonic device: the first two digits of your phone number were replaced by their corresponding letters on a telephone dial. Those two letters were then expanded into a catchy word known as a “central office name”. For example, if your phone number was 555-1234, you’d say “KLondike 5-1234”. Here in the eastern SGV, most phone numbers shared the same prefix: 59. Thus they shared the same central office name: “LYcoming”. Landowners Currier and Mildred Thatcher lived on Lycoming Street in 1957, when it was first name-checked in the press. (It was previously called Lemon Road.) My theory is that they named this street and that – since they had no ties to Pennsylvania – they were inspired by their own phone number: LYcoming 2-7777.