My own 2 cents- my native language being french, I found that I "understood" english much better after learning danish - especially what I previously classified as "weird" (old?) english words like ale (øle), hound (hund) etc.
Learning related languages does help understand the connections between the languages. To continue your example, "dog" in German is also "Hund".
Etymonline says (of hound): O.E. hund "dog," from P.Gmc. hundas (cf. O.S., O.Fris. hund, O.H.G. hunt, Ger. Hund, O.N. hundr, Goth. hunds), from PIE kuntos, dental enlargement of root kwon- "dog" (see canine). Meaning narrowed 12c. to "dog used for hunting."
Expanding that a bit, it says: Old English hund "dog" from Proto-Germanic hundas (compare to Old Saxon, Old Frisian hung, Old High German hunt, German Hund, Old Norwegian hundr, Gothic funds), from Proto-Indo-European kuntos, dental enlargement of root kwon- "dog" (see canine). Meaning narrowed in the 12th century to "dog used for hunting."
It's actually "dog" which is the strange one out. That site elaborates: O.E. docga, a late, rare word used of a powerful breed of canine. It forced out O.E. hund (the general Germanic and IE word; see canine) by 16c. and subsequently was picked up in many continental languages (cf. Fr. dogue (16c.), Dan. dogge), but the origin remains one of the great mysteries of English etymology.
(It looks like dog was applied to what we now call a mastiff, though I'm not sure.)
Since you know French, it makes sense that you find "dog" to be a normal term - apparently it comes from the English (?!) - while you are less familiar with 'hund' and its variants.
