French connaître is, I think, related to the English word 'cognition' (from Latin co + gnōscere 'to know'). The Indo-European (IE) root is sometimes given as *√gn-, sometimes *√gno  from which comes the Sanskrit root √jñā. The IE gives rise to many English words. Via the Greek we get 'gnosis'. From the Latin nōscere (dropping the g) we get 'noble' which original meant '(well) known', from L. nōbilis via Old French noble; similarly 'note' and 'notorious'. 'Quaint' derives from the Old French coint, from L. cognitus, which also gives us 'cognition' and 'recognise'; French variations on L. cognōscent (present participle) give us 'connoisseur', 'cognisance', and 'reconnaissance'. The Sanskrit equivalent of 'cognition' is saṃjñā (sam- and co- both signifying 'together'), though saṃjñā in Buddhist usage often means 'to recognise' or 'apperception'.
Kennen must be related to the English 'ken' from Old English cennan (via Scots dialect) which is again ultimately derived from *√gno. Compare this with the Anglo-Saxon equivalent: cnāwan. The word ken 'to come to know' is also related to the Germanic *kuntha which became Old English cūtha and this gives us the word 'uncouth' which originally meant 'ignorant'.
Savior and wissen however are not cognate, that is they derive from different roots despite having a similar meaning. Savior derives from the Latin sapare 'to taste, have taste, be wise', from which we also get the words 'savant', 'sapient', and our species name 'Homo Sapiens'. Words such as 'savour' and 'savoury' are from the same root. The IE root is *√sep and I have not identified a Sanskrit cognate.
Wissen by contrast is clearly related to words such as 'wise' and 'vision' from Latin visione. The Greek is oida. All are clearly related to the Sanskrit √vid from which we get the cognate vidyā 'knowledge (especially esoteric), science etc'. The idea here is that what we see, we know. Related words are veda 'knowledge', vedanā 'that which is made known'.
The link between knowledge and vision is explicit in Sanskrit and Pāli and they often occur as synonyms. As well as √vid we also find the root √dṛś is used in this way. From √dṛś especially we get the words darśana 'to see' but also 'an opinion', and dṛṣṭi 'seeing, notion, doctrine'. Presumably savior 'to taste' must be being used in a similar sense here. Note that in Buddhism the knowledge associated with views and doctrines is suspect, but this is a sectarian view and does not emerge from philological concerns.
The word 'understand' (the sense of savior and wissen) means 'to stand in the midst'. From IE *√sta (Sanskrit √sthā) and 'under' not used in the usual sense of 'beneath', but deriving from IE *nter 'amidst, among' (cf Sk antar 'between'; and Latin. inter-). The word 'interest' comes from the Latin inter est 'it is among'; compare also 'interior'. By contrast the Sanskrit antargacchati simply means 'to go between', though adhigacchati 'to go over, to approach' can figuratively mean 'to understand'.The Greek for understanding is epistamai 'I stand upon'. Spatial metaphors using 'in' and 'on' are often interchangeable: for instance we can say "in his view", but equally "on this view" (the latter seems more common amongst American academics).
There is another important Sanskrit verb √budh 'to perceive, notice, understand, to awake'. From this word we get the important Buddhist technical terms buddha 'awoken, understood' and bodhi 'awakening, understanding'. We also get the verbal noun buddhi 'intelligence, reason, mind'. The only trace of this word in English is in the word 'bid', as in "do as I bid you" which is related to the causative form bodhaya- 'to inform' via the Anglo-Saxon bēodan 'command'.
The Sanskrit root √jñā is used with a number of affixes: abhijñā 'direct knowing'; prajñā 'wisdom'; saṃjñā 'awareness, apperception', vijñāna 'consciousness'. Not all combinations produce expected results however, compare: anujñā 'allow, permit' (anu = along, with); avajñā 'insult, disrespect' (ava = down, under).
The dictionaries I regularly consult for this kind of essay offer a surprising range of English equivalent for Sanskrit and Pāli words meaning 'to know' indicating the breadth of the concept: 'perceive, apperception, conceive, apprehend, comprehend, understand, cognition, recognise, ascertain, discern, distinguish, discriminate, experience, investigate, discover, intelligent, judge, observe, conscious, aware'.
Note that all the words with -ceive relate to the Latin capere 'to seize'; and those with -hend relate to Latin hendere 'to take hold of'. All the -cern words (including discriminate) are from Latin cernere 'to sift, separate'. Dis- as a suffix means 'apart'.
- Words preceded by an asterisk * are hypothetical or reconstructed by philologists based on triangulating between the various Indo-European languages using what they know about how sounds change in order to propose the underlying word that gave rise to all of the known variations.