Came across this alternative to “flat out” in my student days in the North (of the UK).  Is it a regionalism and how old is it?  I’m thinking perhaps C19th, but Google throws up almost nothing.

Eric Partridge’s Dictionary of Slang and Unconventional English puts it at ca. 1950 and references Douglas Rutherford novels on motor racing. Clarkson also uses it regularly in his motoring show and car reviews.

Does Partridge hazard any origins?

No

Another similar phrase (I recall this from the 70s) is give it some welly, ie put your foot down and go flat out. Googling makes it clear that the phrase has been co-opted and literalized by gardeners now, its meaning being get your wellies (wellington boots) on and start digging. On the evidence of the googlits this sense is the predominant one now, although I’m almost certain the original is still current.

Another similar phrase (I recall this from the 70s) is give it some welly, ie put your foot down and go flat out.

IIRC Wallace says this to Gromit in Curse of the Were-Rabbit, when Gromit is operating the Bun-Vac 6000.

A variation of full chat heard often enough here in Australia is ‘flat chat’, also meaning fast or to the maximum. I can’t find a date for when it was first recorded, but any Aussie would know that “I’ve been flat chat at work” or “We had the car going flat chat and it only did 80k” means that you are very busy and that the car was at its limit.

The OED has 7 noun entries for chat but most of them are obscure, regional, or obsolete.  No mention is made of full chat or flat chat, which I suppose, for want of any better idea, to be related to chat = “talk”, though I don’t see how. (Edit: I’ve never heard either expression in the US.)

In the US, we have the “talk” sense of chat, both noun and verb, and less familiarly it’s also used as a term for a kind of crushed rock, coarser than gravel, and in the names of a some species of birds ("yellow-breasted chat”, etc.).

In the sense of “at maximum speed, rate, or extent” we have full tilt and flat out.  Are these used in the UK and Australia?

I’m reminded of the expression “talking a mile a minute” as a related idea that links speed and speaking.

Full tilt and flat out are both used in the UK. Also full whack.

Watching Top Gear last night (a repeat of an old show) Clarkson used the phrase full chat - I hadn’t consciously heard it before in the UK but I think this is an example of diegogarcity (I watch Top Gear a lot but this is the first time I’ve herd him say it though its been referenced above as a Clarkson phrase)

Dr. Techie - 06 March 2009 09:08 AM

The OED has 7 noun entries for chat but most of them are obscure, regional, or obsolete.  No mention is made of full chat or flat chat, which I suppose, for want of any better idea, to be related to chat = “talk”, though I don’t see how. (Edit: I’ve never heard either expression in the US.)

It could be related to the engine noise: top speed = maximum noise = full chat, from “chatter” => “chat”.  Just a WAG!

Dr. Techie - 06 March 2009 09:08 AM

In the sense of “at maximum speed, rate, or extent” we have full tilt and flat out.  Are these used in the UK and Australia?

Yup, we have them here in the UK.  Flat out is, I suppose from horses, but full tilt?  Where does tilt come from?  Is there some obscure meaning in the OED?

Not so very obscure, although not the first to come to mind. It’s from tilt as a synonym for joust (more familiar as a verb in the phrase “tilting at windmills"). Two knights in a jousting match come riding at each other full tilt.

I did think of that, but didn’t think it could be that old.

Actually, tilt in relation to jousting appears relatively late, not until the 16th century, toward the end of the era when people actually jousted. The OED2’s first cite for full tilt is c.1600.