According to The Random House Unabridged Dictionary of English (1977) the noun "layabout" dates from the period 1930-35.
It's "[a noun] derived from the use of the verb phrase lay about
, [which is a] nonstandard variant of lie about
For many years speakers of English have used the verb form "lay" ("put, place") when they mean "lie" ("be in or assume a recumbent position"). This usage is very common in spoken English but is still considered incorrect. The noun "layabout" was formed from the nonstandard use of "lay" for "lie."
If you're in search of words to describe someone who does nothing, or who makes as little effort as possible, you may enjoy consulting "An Idler's Glossary," a collection of 200 nouns, verbs, and adjectives relating to the practice of idleness, with definitions and comments. It's athttp://www.hermenaut.com/a158.shtml