Blending Two Individual Words Together That Share the Same Consonant Cluster

I've noticed that this phenomenon is common in fast speech. I have searched and searched on the internet for the official name for this, but I cannot seem to find it. Here are some examples:

• With this (pronounced withis).
• Watch Changes (pronounced Watchanges).

These seem to me to be almost like portmanteaus, but they're not. Is this just lazy speech? Does anybody know what this phenomenon is called; I'm just curious.

Thank You.

I can't imagine any other way to say "With this ring, I thee wed" other than withis. On the other hand, "my watch changes every time I look at it" would definitely include two ch sounds. Trying to think of other cases: Where do we wash shirts? Might be said with one prolonged sh sound. I think ch doesn't work because ch includes two sounds (t-sh) How about "Don't talk so loud"? or "I can't tell." There's only one release of the t sound. Calling it "lazy speech" reveals a misunderstanding about how speech and linguistics works. There's no place for pejorative language in describing how people speak. But if you're deeply interested in language, you might want to learn about the standard use of who/whom in your further comment: "I don't of anybody whom would combine those specific words together either." "Whom" is not just an upscale version of "who." It is objective case, while your sentence calls for subjective case. But I hesitate to go pejorative on you.

Here's a link that shows the various things that naturally happen when English is spoken: The particular example of linking that you give seems to be called geminates. https://pronuncian.com/introduction-to-linking/