motherload – a common mistake or slang word?

Question

I am a bit unsure about how the word "motherload" should be seen – as a common mistake or slang word or both. I've encountered the word the first time in a recent Guardian article, but to my surprise it was later changed to "mother lode":

This article was amended on 17 May 2017. An earlier version spelled “mother lode” as “motherload”.

After having seen something like that in a book

Since the dramatic emergence of Prince, however, Minneapolis has yeilded

(sic !)

a rich motherload of new soul music talent.

I am not sure if many uses of "motherload" are actually because of ignorance. The word often appears in a context, even scientific one, which does not really "allow" the usage of slang. The only online dictionary that lists "motherload" seems to be Wiktionary. So I wonder if the intentional use of "motherload" as a slang word is actually rare?

Answer 1

"Motherload" is a non standard spellings of the more common "motherlode".

As suggested by the following source load and lode were originally the same term. Through the centuries they developed different connotations and lode was more commonly used from the 17th century to refer to a rich vein of mineral ore, from which the more common spelling "motherlode" from the 1920s especially in a figurative sense:

• If I sound a bit blasé when I say that, it’s because “lode” and “load” were the same word to begin with. They are, as the Oxford English Dictionary (OED) puts it, “etymologically identical,” one being merely a “graphic variant,” a slightly different spelling, of the other. That’s not to say that the words are interchangeable; the spelling difference between”lode” and “load” has led to slightly different meanings over the years.
• “Lode” and “load” first appeared in Old English, drawn from the same Germanic roots that eventually also produced “to lead” in the sense of “to guide, conduct.” “Load/lode” was also influenced by the separate word “lade,” meaning “to load or burden,” which is now obsolete except in such terms as “bill of lading,” the noun “ladle” and the participle “laden” (“Laden with debt, Larry played Lotto.”).

.......

• The original sense of “load/lode” in Old English was “way, route” or “means of transport.” As the forms diverged in meaning in the 13th century, “load” developed in the sense of “that which is carried,” now familiar in everything from the “load” of a truck to the “debt load” that prompted Larry to gamble.

• “Lode,” however, developed in the “guide, signal” sense, giving us “lodestar,” a bright star in the sky (usually Polaris) used to navigate ships, and “lodestone,” the naturally magnetic mineral “magnetite,” used in primitive compasses.

• In the 17th century, “lode” began to be used to mean a rich vein of mineral ore in the earth that, once discovered, would guide miners in their excavations. Starting in the 19th century, an unusually large and rich lode was known as a “motherlode” (“The lode called the Esmeralda, the most prominent and apparently the mother lode of the district, runs with the meridian.” 1863).

• Beginning in the 1920s, a rich source of anything was figuratively known as a (or “the”) “motherlode” (“The pages of the T.L.S. were the very mother-lode of academic inanity.” 1960).

(www.word-detective.com)