Mem doesn't have pages in BDB about itself - it's מן that does and the preposition when it clings on to a word loses its nun most of the time. This losing of letters cannot be ignored any more. Vav and yod appear and disappear as helpers of reading in full and defective spellings and 'nun' and 'he' appear and disappear if they are part of the root. Will we find examples? Just consider, if I were to look for nun - it wouldn't be there - so how will I find it? I am sure the weak consonants will appear when we need them.
Some things that we do with our gums, lips, teeth and throat are common to all tongues. I bet there is stuff on the web somewhere about sibilants (sounds like s), gutturals (from the throat), dentals (from the teeth), and labials (from the lips) and a bunch of other special terminology. How do the Hebrew letters stand in this area?
These are distracting question so I have pushed my meandering answer to the bottom of the post. Continuing with Ruth ...
Mem as a leading letter meaning 'from' is common
לָגוּר בִּשְׂדֵי מוֹאָב
to stay in the fields of Moab
Ruth 2:1 (similar to 3:2) has an mem prefix to the word know יָדַע thus forming the noun acquaintance.
Ruth 3:4 (sim 3:7, 3:8, 3:14) This word in the plural is again derived from the verb or even the singular noun together with a mem. (In this form only used in Ruth and once in Daniel 10:6)
Addendum - letters and their sound classifications
This summary from Gesesius will save me some thinking - notice the distribution of the first 11 - the green grammatical group. I have a theory that they are 'easier' to pronounce and they make pronunciation of other letters easier especially when things need to be elided (like 'a' and 'an' in English).
|(a) Gutturals||||א ה ע ח|
|(b) Palatals||ג כ ק|
|(c) Dentals||ד ט ת|
|(d) Labials||ב פ|
|ז שׁ שׂ ס צ|
|ו י | ר ל | נ מ|
א - guttural like a glottal stop in English - light
ב - must be a labial
ג - palatal - I can feel the palate 'g'
ד - dental
ה - guttural - light
ו - sonant - never seen this word before and neither has my dictionary! Sounds like it is missing a con as prefix. I think I know it as a voiced consonant. Most of the others are unvoiced except zayin, dalet, and gimel.
ז - sibilant
ח - guttural - heavy duty
ט - dental like its brother taf
י - sonant
כ - palatal (guttural?)
ל - sonant - the middle pair
מ - sonant - the last pair
נ - sonant - the last pair
ס - sibilant
ע - guttural - heavy
פ - labial (fricative?)
צ - sibilant
ק - palatal (guttural?)
ר - sonant - the middle pair - like the gutturals never takes a dagesh
ש - sibilant - ambiguous pronunciation without the diacritical mark
ת - dental