Et al. (from the Latin et alii – “and others”) and etc. (from the Latin etcetera – – “and other things”) are sometimes used interchangeably in error. “Et al.” always refers to people, and “etc.” in almost all situations refers to things other than people.
Preliminarily, note the punctuation: “et al.” The period should always appear after “al”, not ever after the “et”; it is also in error to omit the period (“et al”). And it is not uncommon to see “etc.” misspelled “ect.” Another error in form with both terms is that they often are italicized; they should not be. A final grammatical error is the use of “and” before either of them as the “et” in both terms (meaning “and”) makes it redundant.
Both terms are used excessively; “and others” can be a fair substitute for “et al.”, and “and other things” for “etc.” George Krapp, in “A Comprehensive Guide to Good English” states: “It is easy to end with an ‘etc.’, throwing the burden of finishing the thought upon the reader. . . . If the thought is not adequately expressed, ‘etc.’ will not take the place of that which has not been said. The use of ‘etc.’ tends to become a slovenly habit, the corrective for which is to refrain from using ‘etc.’except in the driest and most documentary kind of writing.”(p.229)
Occasionally it can be effective to double the use of “etc.” to emphasize a great multiplicity of items, as in “For every tone of voice there is a corresponding literary style: hearty, earnest, pensive, shrill, rebuking, strident, whispering, etc., etc.” In fact, it was tripled in the musical “The King and I” (“…etc., etc., etc.!”) to great comic effect, though such multiple use seems to modify the meaning of the word.
– Ken Butera