Navvy is a shorter form of the word 'navigator' and is particularly applied to describe the manual labourers working on major civil engineering projects. The term was coined in the late 18th century in Britain when numerous artificial waterways (canals) were being built. These canals were also sometimes known as 'navigations'.
Typically, the individuals worked with shovels, picks and barrows. Steam-powered mechanical diggers or excavators (initially called 'steam navvies') did not became available until the late 19th century.
The British canal revolution was superseded by a rush to construct railway projects from about 1830 onwards, and the same term was applied to the workmen employed on building railways, their tunnels, cuttings and embankments.
