Origins
The word 'gland' entered English in the late seventeenth century from French 'glande,' which came from Latin 'glans' (genitive 'glandis'), meaning 'acorn.' The anatomical usage arose because early Roman and medieval physicians saw a resemblance between the small, rounded, embedded organs they were dissecting and the shape of acorns. The metaphor was entirely visual: glands are compact, roughly oval or rounded structures nestled in tissue, as acorns sit in their cups.
The Latin 'glans' derives from PIE *gʷelh₂- (acorn), a root with cognates in Greek 'bálanos' (βάλανος, acorn — the initial consonant shifted from *gʷ to b in Greek). Greek 'bálanos' survives in the English botanical term 'balanophagous' (acorn-eating) and in 'balanus' (a genus of barnacles whose shells resemble acorns). The anatomical term 'glans' — referring to the rounded head of the penis or clitoris — preserves the Latin word in its original spelling and original meaning: acorn.
The concept of a 'gland' as a secretory organ developed gradually. The ancient Greeks recognized certain structures as glands — Hippocrates described glands in the neck and groin — but their function was poorly understood. The prevailing theory, from Galen through the Middle Ages, was that glands served to support and protect blood vessels, acting as cushions or packing material. It was not until the seventeenth century that researchers began to understand glands as secretory organs. The Italian anatomist Marcello Malpighi (1628–1694) made crucial observations using the newly invented microscope, and Thomas Wharton published 'Adenographia' (a description of glands) in 1656.
Development
Modern physiology classifies glands into two main types. Exocrine glands secrete substances through ducts onto epithelial surfaces: sweat glands, salivary glands, sebaceous (oil) glands, mammary glands, and the glands of the digestive system (the pancreas functions partly as an exocrine gland, secreting digestive enzymes through the pancreatic duct). Endocrine glands secrete substances — hormones — directly into the bloodstream without ducts: the thyroid, adrenal glands, pituitary gland, pineal gland, and the endocrine portion of the pancreas (the islets of Langerhans). The distinction between exocrine and endocrine was not established until the nineteenth century.
The word 'glandular' (adjective, pertaining to glands) entered English in the eighteenth century. 'Glandular fever' is the British name for infectious mononucleosis — so called because the disease causes pronounced swelling of the lymph glands (lymph nodes). In popular usage, 'glandular' is sometimes used loosely to explain conditions like obesity ('it's glandular'), typically referring to hypothyroidism or other endocrine disorders, though such conditions account for a small minority of obesity cases.
The lymph nodes — small, bean-shaped structures distributed throughout the body — were historically called 'glands' and are still colloquially referred to as such ('swollen glands' in the neck). They are not true glands in the secretory sense but are part of the immune system, filtering lymph fluid and housing white blood cells. The terminological confusion between lymph nodes and true glands persists in everyday language.
Latin Roots
The pituitary gland — a pea-sized structure at the base of the brain — is sometimes called the 'master gland' because its hormones control the function of most other endocrine glands. Its name comes from Latin 'pituita' (phlegm, mucus), because it was once believed to produce the nasal mucus. This is anatomically incorrect — the pituitary has nothing to do with mucus — but the name, like 'artery' (air-vessel), preserves an ancient medical error.