The Old English word for 'barley' was bære, which traces back to Proto-Indo-European and is cognate to the Latin word farina "flour". The direct ancestor of modern English "barley" in Old English was the derived adjective bærlic, meaning "of barley". The first citation of the form bærlic in the Oxford English Dictionary dates to around 966 CE, in the compound word bærlic-croft. The underived word bære survives in the north of Scotland as bere, and refers to a specific strain of six-row barley grown there. The word barn, which originally meant "barley-house", is also rooted in these words.
Barley is a member of the grass family. It is a self-pollinating, diploid species with 14 chromosomes. The wild ancestor of domesticated barley, Hordeum vulgare subsp. spontaneum, is abundant in grasslands and woodlands throughout the Fertile Crescent area of Western Asia and northeast Africa, and is abundant in disturbed habitats, roadsides and orchards. Outside this region, the wild barley is less common and is usually found in disturbed habitats. However, in a study of genome-wide diversity markers, Tibet was found to be an additional center of domestication of cultivated barley.
Wild barley has a brittle spike; upon maturity, the spikelets separate, facilitating seed dispersal. Domesticated barley has nonshattering spikes, making it much easier to harvest the mature ears. The nonshattering condition is caused by a mutation in one of two tightly linked genes known as Bt1 and Bt2; many cultivars possess both mutations. The nonshattering condition is recessive, so varieties of barley that exhibit this condition are homozygous for the mutant allele.
Each plant gets a set of genes from both parents, so there are two copies of each gene in every plant. If one gene copy is a non-working mutant, but the other gene copy works, the mutation has no effect. It is only when the plant is homozygous, i.e. both copies of the gene are non-working mutants, that the mutation shows its effect, i.e. the plant exhibits the nonshattering condition.