By 1680, Lake Simcoe appeared as Lac de Taronto on a map created by French court official Abbé Claude Bernou; by 1686, Passage de Taronto referred to a canoe route tracking what is now the Humber River. The Humber River became known as Rivière Taronto as the canoe route became more popular with French explorers, and by the 1720s a fort to the east of the mouth of the river was named Fort Toronto.

The change of spelling from Taronto to Toronto is thought to originate on a 1695 map by Italian cartographer Vincenzo Coronelli.

Pronunciation
The stress is on the second syllable. Locals sometimes pronounce the city's name as "Toronno" (most often, as in 'I'm gonna go to Toronno') or "Tronno", "Tronto", "Toranna", "Taranna", "Chronno" or "Chranna" (both with ch as in chime, not chrome) or even "Terawhnna". This is a reflection of the varieties of Canadian pronunciation and does not represent a unique pronunciation for the city name itself. Even the same local speaker may pronounce the name differently depending on the subject of the conversation in which it is used.

For instance, many Canadians pronounce the number "ninety nine" as something between "9-D-9" and "9-E-9", pronouncing the "t" as an alveolar tap, whereas many Britons or East Indians will distinctly pronounce "9-T-9". Thus while it is natural that many Canadians will say "Toronno", speakers whose dialects pronounce the "T" distinctly in words like "ninety nine" should do likewise when pronouncing "Toronto". In each case, the speaker merely pronounces "Toronto" in the way that is most natural in his or her dialect. Some Torontonians would often identify a local if he/she says "Toronno".

Even for Canadian speakers it is never outright incorrect to pronounce distinctly the second t in Toronto. Pronouncing it "Tor-on-toe" (with stress on the second syllable) in casual speech is usually seen as a sign of someone who is not a native of the city. Canadian francophones pronounce it, "To-ron-to", in three syllables, with the french nasal on on the second syllable, and the accent on the third syllable.

Nicknames
Toronto has garnered various nicknames throughout its history, including:
T.O. – an acrostic for Toronto, Ontario, or a false acrostic for Toronto; pronounced "Tee-Oh" 
T-Zero - a play on the T.O. nickname used by anti-Torontonians (often Montrealers) 
T-dot or T.dot – short for "T-dot, O-dot", a hip-hop slang nickname for Toronto 
The Big Smoke – a nickname it shares with many other cities 
The Centre of the Universe - A derogatory term used outside Toronto. 
Hogtown – referring to its importance in the 19th century as a site for growing, trading, and marketing livestock. 
Toronto the Good – from its history as a bastion of 19th century Victorian morality (sometimes called Toronto the Bad now in reverse as a derogatory nickname) 
Methodist Rome – an analogy implicating the city as a centre for Canadian methodism, akin to Rome's role in Catholicism 
City of Churches 
Hollywood North – due to the many TV and movie productions in the city (although this title is also given to Vancouver) 
Queen City – a reference most commonly used by francophone Quebecers ("La Ville-Reine") 
Muddy York – derived from Toronto's previous name, York, and the weather's effect on its once-largely unpaved streets 
The 416 – 416 is the original telephone area code for much of the city (the other area code in Toronto is 647; 905 is used in the surrounding GTA exurbs) 
The Economic Engine of Canada.
New York run by the Swiss – a take on Peter Ustinov's oft-quoted reference of the city to reporter John Bentley Mays in The Globe and Mail on 1 August 1987: "Toronto is a kind of New York operated by the Swiss." When reminded of this later at a reception in June 1992, he responded (again cited in The Globe), "I've learned it's really run by the Canadians." 
Tehranto, a portmanteau of Tehran and Toronto.