Here is a list of all namespaces with brief descriptions:

[detail level 12345]

nano_cff
nano_eras_cff
nanoaod
flatTableHelper
NanoAODEDMEventContent_cff
nanoDQM_cff
nanoDQM_cfi
nanoDQM_tools_cff
nanoDQMIO_perLSoutput_cff
nanogen_cff
nanogenDQM_cff
NavigationSchoolESProducer_cff
NavigationSchoolESProducer_cfi
NbTarget_cfi
NearbyPixelClustersProducer_cfi
negativeCombinedInclusiveSecondaryVertexV2BJetTags_cfi
negativeCombinedMVAV2BJetTags_cfi
negativeCombinedMVAV2Computer_cfi
negativeCombinedSecondaryVertexV2BJetTags_cfi
negativeCombinedSecondaryVertexV2Computer_cfi
negativeOnlyJetBProbabilityBJetTags_cfi
negativeOnlyJetBProbabilityComputer_cfi
negativeOnlyJetProbabilityBJetTags_cfi
negativeOnlyJetProbabilityComputer_cfi
negativeSimpleInclusiveSecondaryVertexHighEffBJetTags_cfi
negativeSimpleInclusiveSecondaryVertexHighPurBJetTags_cfi
negativeSimpleSecondaryVertexHighEffBJetTags_cfi
negativeSimpleSecondaryVertexHighPurBJetTags_cfi
negativeTrackCounting3D2ndComputer_cfi
negativeTrackCounting3D3rdComputer_cfi
negativeTrackCountingHighEffBJetTags_cfi
negativeTrackCountingHighPurBJetTags_cfi
NeutronBGforMuons_cff
NeutronBGforMuonsHP_cff
NeutronBGforMuonsXS_cff
neutronHitsCollector_cfi
neutronSimHitsProcessing_cff
newFWLiteAna
nJettinessAdder_cfi
NMaxPerLumi_cfi
noAbortPDGid_custom
NoBPTXMonitor_cff
NoBPTXMonitor_cfi
NoCQTask
NoHcalZeroSuppression_cff
NoiseFromExampleXmlFile_cff
NoiseRatesClient_cfi
noiseSimValid_cff
noPuUtils
notcub	CUB namespace
noZS
npstat
Private
ntuple
ntuple_cff
ntuple_cfi
ntupleDataFormat
ntupleEnum
ntuplemaker
ntuplePlotting
ntuplePrintersDiff
NuclearSeed_cfi
NuclearTrackCorrector_cfi
numberPerLSFilter_cff