What is the nuance of ‘Slipping’ when you say ‘I started slipping my classes short writing assignments?’

Question

I found an op-ed article titled ‘Teaching to the Text’ in today’s New York Times (www.nytimes.com/2011/03/20/opinion/20selsberg.) interesting as a non-native English learner. However, I stumbled on a phrase, ‘slip someone an assignment’ as used in the following sentence, as the word, ‘slip’ appears to be used to me in very different way from I usually use - such as ‘slide a short distance accidentally’ or ‘go / put quickly’ as defined by COD.

Can somebody explain me what nuance does the word ‘slip’ have in this particular sentence? Is ‘slip’ used in this way very often?

‘I don’t expect all my graduates to go on to Twitter-based careers, but learning how to write concisely, to express one key detail succinctly and eloquently, is an incredibly useful skill, and more in tune with most students’ daily chatter, as well as the world’s conversation.’ So a few years ago, I started slipping my classes short writing assignments alongside the required papers. Once, I asked them, “Come up with two lines of copy to sell something you’re wearing now on eBay.'

Answer 1

The metaphorical use of 'slip' is pretty common.

• You can 'slip someone a mickey' (surreptitiously give them a much more inebriating drink than ordered so that they lose control (for nefarious purposes) (you can 'slip someone' any sort of intoxicating substance/drug).

• You can 'slip someone' some money, that is, handed them a little cash with the connotation that you're not doing it openly (not necessarily nefariously, just not in front of others

• Something can 'slip by you', if you forgot something recently.

Answer 2

The meaning of to slip in this example comes from the transitive verb definition #6 in Merriam-Webster:

to insert, place, or pass quietly or secretly

It means that the instructor was including these kinds of assignments as a subtle way to teach students how to write concisely.

Another, more direct, example would be to slip someone a twenty dollar bill as a bribe:

I immediately got a table at the restaurant because I slipped the greeter a twenty.