Some words in English inexplicably have a defined meaning and then also mean the exact opposite of that meaning. These are known as contronyms or Janus words – the latter derived from the Roman god of beginnings and endings, often depicted with two faces looking in opposite directions).
1.Sanction
To give official permission or approval for an action.
To impose a penalty upon someone/something.
2.Oversight
A verb meaning to oversee, derived from Old English ofersēon: to look from above.
A verb meaning to overlook or to pass over without noticing.
3. Dusting
If you dust crops you add chemicals.
If you dust furniture you remove dust particles.
4. Trimming
Derived from Old English the verb to trim means to make firm, strong, settled or arranged; i.e. a Christmas dinner with all the trimmings.
However trimming as a verb refers to paring back or pruning overgrown trees – the opposite.
5. To cleave
One form of the verb derives from Old English and means to cling or adhere to something. (cleofian, clifian, or clīfan.)
The other form of the verb to cleave comes from a past participle of the word: cloven. You would know the term cloven hoof. This is the other meaning of cleave: cloven/separated.
6. Fast
Fast generally means moving rapidly or at speed.
Yet colours, glue and materials can be held fast in one place. The latter meaning derives from the term steadfast.
7. Clip
You can clip sheets or papers together to be bound. This comes from Old English: clyppan, to clasp with the arms, embrace or hug.
However you can also clip away or snip parts of an object away. The latter meaning comes from the Old Norse word Klippa meaning the sound made by shears.
Content Catnip 
When we realize the double meanings of words such as these, we can think about how difficult and confusing it must be to learn English as a second language.
LikeLiked by 1 person
Totally yes! English is littered with all of these little landmines that are annoying. For example a friend of mine says “hairs” to describe her hair as a whole, as in “my hairs are getting long” which logic would say would be correct but it is infact that opposite. When you pull at a few strands of hair it is called “hairs”, whereas your whole head of hair getting cut is referred to as “cutting your hair”…yet another example of how ridiculous English is!
LikeLike
Oh this is an amazing post 🙂
I’d not thought about these before, brilliant!
Oh our dualistic world!
xxx
Niki
LikeLiked by 1 person
Hey Niki, thank you so much I am so glad you found it interesting. I know how strange the language is, there are so many weird quirks, so glad I’m a native speaker and not trying to learn it.
LikeLiked by 1 person