Place-names in Germania

Hi,
can anybody see if these etymologies of place-names in ancient Germania
(all from Ptol.) sound correct ?
Marnamanis p., i) mar-no < *mar- 'sea', ii) germ. *manni < *ma-no- 'wet'
--> 'torrent that goes in the sea'
Brodentia, i) brod- < *bhRdh- 'ford'. Can it be proved to be germanic ?
Calisia, i) cal-, germ. (*g > k) < *gwolo- 'land, region', cfr. lith.
galas, thrac. *kalas 'district' (Duridanov)
Menosgada, i) men- ?, ii) osga < *ud-sko '(related to) water', ii) -da <
*dhA '(that) gives' --> 'that gives ? water'
Riusiava, i) rius- < *reus-/rus-, cfr. thrac. *rusa 'pit', balt. rusa 'id.'
(Duridanov), ii) ava < germ. *a(g)wja > -avia in classical authors, cfr.
Scandin-avia < *akw- --> 'water of the pits'
Semanus silva, i) seman-, germ. (*o > a) < *sei-mon, cfr. thrac. *Saiman
'ridge', gk. Haimon, Haemus < *sei- 'to bind' (?)
Strevinta, i) strev- < *sreu- 'to flow'. Can it be proved to be germanic ?

Also Asciburgium, Tulifurdum and then Tulisurgium sound germanic to me, but
what can be Ausci-, Tuli- and -surgium ?

The presence of /f/ makes germanic some names such as Lupfurdum, Fabiranum
and Leufana, but from which words or IE roots ?