The first helots were Laconians that Sparta defeated and conquered. The etymology is uncertain -- there have been numerous suggestions -- but the likeliest explanation is a relation to the root *ἑλ- (cf., ἁλίσκομαι "to be captured"). Sparta conquered Messenia around 640 BC–620 BC; the enslaved Messenians formed the bulk of the helots.
Helots lived in their master's household but were owned by the state; unlike ordinary slaves, their master could not declare them free. They served as agricultural and domestic slaves, and sometimes military servants as well. Spartans usually allowed agricultural helots, the backbone of Lacedomanian agricultural production, to keep excess produce.
The helots outnumbered the Spartans by some unknown ratio, most probably in excess of a typical ration between normal chattel slaves and freemen in other Greek communities. Herodotus reports (Book IX, 10) that seven helots accompanied each Spartan hoplite to the battle of Plataia in 479 but this figure is often doubted by modern scholars. Fearing rebellion, the Spartans continually kept themselves militarily prepared to crush any uprising, and hesitated to join military campaigns far from Sparta. An annual ritual pillaging by adolescent Spartans, known as the Krypteia, also served to keep the Helots in line. According to Aristotle, the Spartan ephors annually redeclared war against the Helots to justify the use of force against them.
In wartime helots served as light infantry and as rowers in ships. During the Peloponnesian War they also fought as heavy infantry, and helots who excelled in battle could earn their freedom. Some 2000 were freed and reputedly later assassinated.