american english - Why do some words have two past tense forms (e.g. "dreamed" vs. "dreamt")?

While perusing ShreevatsaR's answer to this question, it occurred to me that my own verbal usage is out of step with what I see in current American literature. When speaking in the past tense, I prefer to use the following forms:

• dreamt (past tense of to dream)


• leapt (past tense of to leap)


• swept (past tense of to sweep)


• lit (past tense of to light)

However, when reading recently written novels, I see the more regular conjugation of the past tenses, which instead yields dreamed, leaped, sweeped, and lighted. Is it a difference of dialect (US - New England), register (university education), or (possibly) my age (early forties)? I am especially irritated by "lighted" because it takes so much more effort to say than "lit".

CLARIFICATION: Given Jon Hanna's answer below, I would just like to clarify the question a bit more. What I was originally after was why these separate verb forms exist in the same past tense. In other words, variations such as "I dreamt" vs. "I dreamed", not the variation between different forms in different pasts. I am not a linguist, so I hope that clears things up a bit.

Answer

I did some research using the Corpus of Historical American English to see if I could track the history of these words. Each of these words has a different story to tell.

DREAMED and DREAMT

See the raw data (Google Docs)

In the early 1800s, dreamt was more common than dreamed but by the mid-1800s, dreamed was much more common and has stayed so since. While there is nothing wrong with continuing to use dreamt, dreamed is definitely the more common form.

LEAPED and LEAPT

See the raw data (Google Docs)

Leaped has long been more popular than leapt, though leaped has been in decline since 1900, and leapt has been on the increase since 1950, and today they are about equally common. It is likely that if the current trends continue, leapt will become decisively more common than leaped within a decade or two. Indeed, in the Corpus of Contemporary American English, leapt has 484 incidences for 2005-2010 and only 460 for leaped. So, both are about equally common these days and you are in good company if you prefer leapt.

SWEEPED and SWEPT

Neither COCA nor COHA have any results for sweeped, nor does any dictionary I checked list sweeped as a possible past tense form for sweep. Sweeped doesn’t appear to have had any currency in American English since 1810. Google reports only 43,000 results for sweeped compared with 78,000,000 for swept.

LIGHTED and LIT

See the raw data (Google Docs)

Apparently, lighted was much more popular than lit, from the early 1800s until about 1940. During this time lit was steadily gaining popularity, while lighted began a precipitous decline in 1940. Today, lit is much more popular than lighted, so if you prefer lit, you are in very good company. However, there would be trouble objecting to lighted on historical grounds, as lighted was by far the most common form until the 1940s.