Bristol was a starting place for early voyages of exploration to the New World. On a ship out of Bristol in 1497 John Cabot, a Venetian, became the first European since the Vikings to land on mainland North America. In 1499 William Weston, a Bristol merchant, was the first Englishman to lead an exploration to North America. At the height of the Bristol slave trade, from 1700 to 1807, more than 2,000 slave ships carried an estimated 500,000 people from Africa to slavery in the Americas. The Port of Bristol has since moved from Bristol Harbour in the city centre to the Severn Estuary at Avonmouth and Royal Portbury Dock.
The most ancient recorded name for Bristol is the archaic WelshCaer Odor (the fort on the chasm), which is consistent with modern understanding that early Bristol developed between the River Frome and Avon Gorge. It is most commonly stated that the Saxon name Bricstow was a simple calque of the existing Celtic name, with Bric (meaning a break) a literal translation of Odor, and the common Saxon suffix Stow replacing Caer. Alternative etymologies are supported by numerous orthographic variations in medieval documents, with Samuel Seyer enumerating 47 alternative forms.
The Old English form Brycgstow is commonly used to derive the meaning place at the bridge. Utilizing another form, Brastuile, Rev. Dr. Shaw derived the name from the Celtic words bras (quick, rapid), or braos (a gap, chasm,) and tuile (a stream). The poet Thomas Chatterton popularised a derivation from Brictricstow linking the town to Brictric, the last king of Wessex. It appears that the form Bricstow prevailed until 1204, and the Bristolian 'L' (the tendency for the local dialect to add the sound "L" to many words ending in a neutral vowel) is what eventually changed the name to Bristol.