PowerShell code to map CDN (Classic or FrontDoor) to their Origin hostname.

Get-Origins.ps1

Import-Module Az
Connect-AzAccount

$ipre = "^((25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$"

function Get-ClassicOrigins() {
    $profs = Get-AzCDNProfile
    $coll = @()

    foreach ($prof in $profs) {
        $eps = Get-AzCdnEndpoint -ResourceGroupName $prof.ResourceGroupName -ProfileName $prof.Name
        foreach ($ep in $eps) {
            $origin = $ep.Origin.Hostname
            if ($origin -match $ipre) {
                $domain = "IPADDRESS"
            } else {
                $domainspl = $origin.Split(".")
                $domain = "$($domainspl[-2]).$($domainspl[-1])"
            }
            $coll += [PSCustomObject]@{
                AzureDomain = "$($ep.Name).azureedge.net"
                OriginHostname = $origin
                OriginDomain = $domain
            }
        }
    }
    return $coll
}

function Parse-FDData {
    param (
        [string]$FrontDoorOriginGroupName,
        [string]$ResourceGroupName,
        [string]$ProfileName
    )

    $info = @()
    $fdo = Get-AzFrontDoorCdnOrigin -OriginGroupName $FrontDoorOriginGroupName -ResourceGroupName $ResourceGroupName -ProfileName $ProfileName
    $hostname = $fdo.Hostname
    #Write-Output $hostname
    $domainspl = $hostname.Split(".")
    $domain = "$($domainspl[-2]).$($domainspl[-1])"
    if ($FrontDoorOriginGroupName -like "*-Migrated*") {
        $t = $FrontDoorOriginGroupName.Split("-")[0]
        $AzureDomain = "$($t).azureedge.net"
    }
    else { $AzureDomain = $FrontDoorOriginGroupName }

    return [PSCustomObject]@{
        AzureDomain = $AzureDomain
        OriginHostName = $fdo.Hostname
        OriginDomain = $domain
    }
}

function Get-FrontDoorOrigins() {
    $fds = Get-AzFrontDoorCdnProfile
    $coll = @()
    foreach ($fd in $fds) {
        $fdogroup = Get-AzFrontDoorCdnOriginGroup -ProfileName $fd.Name -ResourceGroupName $fd.ResourceGroupName
        if ($fdogroup.Name.Length -gt 1) {
            foreach ($fdog in $fdogroup.Name) {
                if (-not [String]::IsNullOrEmpty($fdogroup.Name)) {
                    $coll += Parse-FDData -FrontDoorOriginGroupName $fdog -ResourceGroupName $fd.ResourceGroupName -ProfileName $fd.Name
                }
            }
        }
    }
    return $coll
}

Write-Output "[*] Getting Classic CDNs"
$coll1 = Get-ClassicOrigins

Write-Output "[*] Getting Front Door CDNs"
$coll2 = Get-FrontDoorOrigins

Write-Output "`n`n"
$final = $coll1 + $coll2
$final | Sort OriginDomain | Format-Table