block (n.) Look up block at Dictionary.com
"solid piece," c.1300, from Old French bloc "log, block" of wood (13c.), via Middle Dutch bloc "trunk of a tree" or Old High German bloh, from a common Germanic source, from PIE *bhlugo-, from *bhelg- "a thick plank, beam" (see balk).

Meaning "mould for a hat" is from 1570s. Slang sense of "head" is from 1630s. Extended sense of "obstruction" is first recorded 1640s. In cricket from 1825; in U.S. football from 1912. The meaning in city block is 1796, from the notion of a "compact mass" of buildings; slang meaning "fashionable promenade" is 1869.
BLOCK. A term applied in America to a square mass of houses included between four streets. It is a very useful one. [Bartlett]
block (v.) Look up block at Dictionary.com
"obstruct," 1590s, from French bloquer "to block, stop up," from Old French bloc (see block (n.)). Meaning "to make smooth or to give shape on a block" is from 1620s. Stage and theater sense is from 1961. Sense in cricket is from 1772; in U.S. football from 1889. Related: Blocked; blocking.