The cities of the immediate East San Francisco Bay Area, familiarly known as "the East Bay," which are serviced by the 510 area code. The most notable of these are Oakland and Berkeley, CA however 510 includes every city which touches the San Francisco Bay from Berkeley in the North down to Fremont in the South and includes other inlying cities such as Castro Valley and Piedmont. Some older user of the term (35+ yrs of age) also consider the further inlying cities of Contra Costa County (area code 925) as inclusive, since prior to the 1990's 510 covered that area as well, however it predominant use today is referencing just the Alameda County cities currently serviced by 510. The area code 510 translates as: 5 = five, 10 = dime, hence the name "the five & dime."
"We hail from the five and dime."
"He's one of those bridge and tunnel folk from the five and dime." (something a San Francisco native might say)